[en] Space radiation is composed of many kinds of energetic particles, in which alpha particle is an important part. So, materials should be studied to protect from this kind of particles for deep space exploration. In this paper, using Monte Carlo method we have simulated high-energy alpha particles' interaction with different materials like aluminum, polyethylene, water, and liquid hydrogen. Aluminum is not the best material to protect astronauts from space radiation according to the production of secondaries and the relation between projectile energy and range. And Bragg peak comes out at the end of the trajectory. (authors)

[en] The fast neutron detector using boron-lined ionization chamber was developed. The Bonner multi-cylinder neutron detector consists of a φ40 mm × 200 mm boron-lined ionization chamber cladding with high density polyethylene cylinder, which was used as fast neutron moderator and with external diameters of 55 , 80, 130, 220 and 285 mm. The energy range of neutrons is broad, extending from thermal neutron to tens MeV fast neutron. The response function of Bonner multi-cylinder neutron detector was simulated by Geant4 code. The experiments based on the standard neutron source were done. While the outer diameter of high density polyethylene is 220 mm, the neutron sensitivity of Bonner multi-cylinder neutron detector reaches a level of 8.702 × 10-"1"5 A · cm"2 · s under experimental conditions. The experimental data were compared with the simulation results. It is shown that the simulation results are accordant with experiment results in observation data error. (authors)

[en] A boron-lined ionization chamber used in n/γ mixed field with better performance was developed. The boron-lined ionization chamber consists of two cavity rooms with the same size: One is for γ, the other is for both γ and neutron. The neutron sensitivity reaches a level of 9.2 × 10-¹⁶ A/(cm^-2 · s-¹) with a calibrated Am-Be neutron source with neutron intensity estimated to be 2.7 × 10⁷ s^-1, and the γ sensitivity reaches a level of 7.36 × 10^-16 A/(MeV · cm^-2 · s^-1) with a calibrated ¹³⁷Cs source with 5.24 μGy/h dose rate. The plateau length is 600 V and the slope is less than 4%/100 V. An average γ compensation coefficient is less than 5% at work voltage of 400 V, which can be used to monitor the n/γ mixed field around reactors. (authors)

[en] In our previous experiment on CR-39 detectors, we found out that bulk etch rate of irradiated area is different from unirradiated area. Therefore, the traditional etching model should be revised. In this case, our modification which based on the theoretical studies printing out and the AFM observation was put forward and new etch rate : V'=V_t/V_irr, was defined. Then, modified track-diameter kinetics was used to clarify AFM analysis. In this research, the key parameters for 100 MeV Silicon ion include V_t=4.12 μm/h, V_irr=2.55 μm/h, V'=1.62, θ=61.03°. And the bulk etch rate V_b=1.58 μm/h. So the etch rate can be calculated whose value in V=2.61>V’. (authors)

[en] Water-soluble chitosan oligomers with different molecular weight were prepared by a γ-ray degradation method. Effects of irradiation conditions on the chitosan degradation, molecular weight of the irradiated chitosan and yield of the water-soluble products were studied. G_d value of the chitosan radiation degradiation was calculated, and mechanisms of the degradation were discussed. Gel permeation chromatography, Fourier transform infrared spectroscopy and ultraviolet-visible spectrometry (UV-VIS) were applied to characterized and analyzed the degradation products. The results indicated that molecular weight of the degraded chitosan decreased remarkably and its chemical structure changed. It was considered that OH radical is vital to the radiation degradation of chitosan. (authors)

[en] The observation of CR-39 Solid State Nuclear Track Detectors is an essential part of analysing its track structure and dosimetry. Proceeding from the theory of latent tracks' formation and growth in CR-39 detector, is discussed the effect factors of etched tracks, and studied the characteristics and contrast of two chosen track reading methods, which include the optic method and electronic microscope method. Based on this, the experiment was applied. The CR-39 detectors, which were irradiated by Si ions with energy of 100 MeV and different fluence, were etched in NaOH etchant (70℃, 6.2 N) for 6 hours and 5 minutes separately. The tracks enlarged and in nano-scale were observed under optic microscope and Atomic Force Microscope. Moreover, bulk etch was measured with partial masked and surface profiler, and the bulk etch rate V_b=1.53 μm/h was got. (authors)

[en] Electrical field in cylindrical proportional counter (PC) was analyzed by using Diethorn formula. It can be seen that multiplication in homemade cylindrical PC happens within the range of less than 30 μm from anode. The lowest operating voltage of the PC is 370-670 V, and it increases with the diameter of both anode and cathode, but changes slowly with the latter. A thinner anode can lead to stronger field around itself, and a lower working pressure will lead to larger mean free path. Both of them can improve the multiplication factor due to the generation of more can more secondary electrons in PC. Selecting a thin anode and low working pressure can not only reduce the lowest operating voltage, but also optimize the performance of amplification of PC, which makes it more suitable to measure radiation dose in deep space. (authors)

[en] The room temperature d⁰ ferromagnetism origin is still highly controversial in oxide systems, due to the lack of subtle experimental set-up as well as sensitive defect detection. Herein, we developed O-rich treatments on Ceria nanocrystals, H₂O₂ and O₂ ambient exposure, which creates intrinsic O defects without introducing trace level of impurities or changing crystallinity. Interestingly, results found that significant oxygen adsorption along with distinct augment of RT ferromagnetism were observed after both H₂O₂ treatment and O₂ ambient exposure. The more the oxygen molecule adsorbed, the stronger the ferromagnetism was. Furthermore, Electron Spin Resonance (EPR) results illustrate that the Ce³⁺ concentration experienced reverse variation in H₂O₂ treated-and O₂ exposed-samples, thus excluding the possibility of Ce cation as the cause of the ferromagnetism. Similar magnetism enhancements were also observed in La₂O₃, ZrO₂ and SrTiO₃ nanocrystals after H₂O₂ treatment. Based on these results, we surmise that the interstitial oxygen, rather than the other sources, facilitated the electron transfer and the dilute ferromagnetism of CeO₂. This work established a general model in clarifying the origin of the disputed ferromagnetism in metal oxide system. - Highlights: • The d⁰ ferromagnetism origin in CeO₂ was studied by O-rich treatments. • Both H₂O₂ treatment and O₂ exposure significantly boost the dilute ferromagnetism. • We illustrated that the interstitial oxygen facilitated the electron transfer and the dilute ferromagnetism of CeO₂.

[en] Formulas for detection efficiency and sensitivity of plate boron-lined ionization chamber were derived from its working principle, and their values for thermal neutrons were obtained. The saturated value of the detection efficiency for thermal neutrons of ionization chamber is 1.35% and the sensitivity is 9.65 x 10^-14 A·cm^-2·s^-1, which approximately coincides with the result of 8.43 x 10^-14 A·cm^-2·s^-1 given by a known formula. Contribution of α particles to the detection efficiency shows small difference with Li ions while that to the sensitivity is predominating. A suitable thickness of boron film, slowing fast neutron and using enriched boron can improve both detection efficiency and sensitivity of boron-lined ionization chamber. (authors)

[en] Three materials wherein suitable proportion of isotope enriched "1"0B powder, 1, 2-ethylene dichloride and formvar resin were blended to make "1"0B neutron sensitive coating by oneself. A new type proportional counter that coated with "1"0B neutron sensitive coating was made. Furthermore, in order to increase the character and quality of the neutron detector, a set of 14 annulus epoxy sheets which were sided with "1"0B film were placed in the tube. A series performance tests were done by "2"4"1Am-Be neutron source. The tests of 3.7 × 10"9 Bq "2"1"1Am-Be neutron source show that the plateau length of detector is 150 V from 750 V to 900 V, while the plateau slope is 8.2%/100 V. When the working voltage is 800 V, the count rate of new type boron-coating proportional counter is 50 s"-"1. The level of sensitivity is 0.71 cm"2. Compared with the detector only coated with "1"0B film in the inner walls of detector, neutron sensitivity area of the new detector increases to 3.15 times. The results show that the plateau length increases from 80 V to 150 V, and the plateau slope is improved from 12.4%/100 V to 7.58%/100 V, while the neutron sensitivity increases to 2.63 times. Using Geant4 software based on Monte Carlo method, this paper presented the response and detection efficiency of new type boron-coating proportional counter, which was covered with φ55 mm × 250 mm cylinder high density polyethylene moderator material. The simulation results of Geant4 are in agreement with the results of "2"4"1Am-Be neutron source experiment. It shows the reliability of simulation application. (authors)